Metering circuit for X-ray machines



Sept. 20, 1949. L. WEISGLASS METERING CIRCUIT FOR -X-RAY MACHINES Filed March 22, 1946 2 Sheets-Sheet 2 40 -2 g 5 I 24 4} L 39 j I 41 FIE-13 J'NL/ENTUH Lou/a L. WE/JGLAJJ id M 2 ATTORNEYJ Patented Sept. 20, 1949 Maintains:cmcmrr nxecanmc.

Picker.xeltaylcormr i M Louis ,Weisglass, -.N.ew York, N.-: Ya, mma u e tion of Ohio.-.

ApplinatiomMarchZZ, 1946; Serial 110265652};

energized:-throughila-ltransiormer andzrecti'fayi i indicatedfby .the; leads;-

circuit in. 'the usual mannere The transformer. has a split-secondarwandithe presentinytention contemplates :the use; of.: a; mechanical 'grectifier in the: groundedi centralx ss'econdary; transformer.

' circuit :whiclr provides: switching; means ion per-.1.

mitting :therectifieds current- .to; .flowein, half e cycle :in-phase withlthescurrent flow toethe ;X;ra g, tube,thus talringiarliiantagenofsthei factthat. the; capacity currentialeadsstheitubeicurrent; by ninety degrees, andiitl'res positive: and negative. com: ponents-cisthewapacity current, may-she; caused; to cancelueaclr-zother; makin eit-pcs ihle; ma h?- tamer-correct 'measuringrof-atheltube current v Other objectseand:aadvantagesuof; the present invention willzheeapparent fromfihemceomrsnr: ingi drawings iandzidescription z and the SSQQUEilu features:thereflfi.willihgiisefi.zffili hjll lihfi amended 1i claim-. a y

In theldrawings form of; inventiom utilizing a; mechan cal: rectifier ore thE: -1DtaEy type v w Fig .2his1a:diagram:illustratingihfil lailmn llipiz of the X-ray tube load currentcand. th e c apacity curren-t during a measuring cycle; while Fig. 3 illustrates a modification of my invention in which avibratory'rectifieris used.

yr inyentioniis sdisqlosesizrie c nnection wit an X-ray tube I'll having a fila t H anglare, anode I2. manner from an alternating current electrical source-I31; L2 connected toethemrimary i31Q-: Of';a i transfcrmen.-l-3.. Thessecondary; of theytrans for-mer I 354's connected-,ahy.-leads ;.l4 andzl 5 gtoga rectifying bridgecircuit includes t, the rectifier-tubes 16 [-1, lLandulSa The rectified current is fed to the tube through the leads 2:! and 2|. The filament I! may be heated in a known manner through transformer 22 supplied with current from the source L3, L4. Those familiar with this type of equipment will understand that means is provided for varying the current at the source Ll L2 as by means of a step autotransformer which it is not necessary to show here.

As modern X-ray machines are built entirely shockproof, that is, with all leads carrying high tension being heavily insulated, a milliammeter for reading the current supplied to the tube is tull is supplied in the usual 3 2 generally insert circuit;

e e ondaryswinsiine {I 312 ir igh e o transformer?isnthhmf r n i t ham e s as of:- measuring: thegstuhe leads nectedibetweeni'ii'ieileads .4

load) butsalscireadsileakaae currentsandmpac ity currents; Thezexistencego capacityebetween,

the-high: tens-ion;coilslandiground isiunavoidable.

15.; These capacitylcurrentsiarerofj-substantial y ubev'load currents and therefore; greatly. disimt:thesmeasutement;

same magnitudeaaseth'eaxe'rayi.

of actual tub eloadacuraentiat:this;point, At

tempts havebeam made imthm .past 1130,; use. compensation currentsitwdiminishwomeliminate, this undesirable: errant. 'liheepresentxinyention. provides another-solutiom departing from :the; prime ciple offcompensatioms a I Referring-tame;-1, thesleadmfihcormnunicates. Fig. l zisira-l diagrammaticwiemillustratine;one; by m sarsuiwblei-brush wim'thevslipring 25 of; a; mechanical rectifiemof 'the rotary type.

This;-ring=-in turn--is-conneetectiby lead 2.6 .to; a. Bruslrdfl'; shown-in contact.

lead iron-1 the meten -3 l communicates through brush SZ-"With halfirinQ fl which in turn-is connectedpy-lead fletoslip ringt which, bylmeansorea suitable-brush; communicateswith lead; 2:1;

The reetifier i's rotated by -means of synchronous- 11101701 36, a -shaft ccnneetien -fl being indicated:

36 is-suppli3edifi om theseurce I31 IiZ, the same 4 ;source as is connected -tmthe;transformerprimary I 3a. Means is prpvided foi gadjustingwthe phase -angle-of the rectifier-withrespectto the phase angle of the X-ray tube current. The means here shown comprises a friction type clutch 38.

The action of this rectification in the central secondary circuit of the transformer is diagrammatically illustrated in Fig. 2. It should be understood that a mechanical rectifier acts as a contact closer for a controlled time, thereby peras will be as indicated in the curve A of Fig. 2, and.

statr e r uerieds p t he e chs 102; so; 1ocatedein..thee prim a ts ndicat s.=;-. ot;=- l v the actual tube current (transformer in-phase;

the integrated value of this current is indicated by the area shaded by vertical lines. It is a well known fact thatthe capacity current is ninety degrees out of phase with the tube load current indicated at A and leads the latter during the half cycle measured. This capacity current is indicated by the curve-B, Fig. 2,,.and its integrated value is indicated by the "areas shaded with horizontal lines. Obviously, during this half cycle, this capacity current has equal integrated areas, plus and minus, therefore the resultant integrated value of the capacity current is zero. This leaves only the X-ray tube load current in-phase as shown by thearea beneath the curve A as flowing in the circuit 29, 39, 3|. It is true that slight leakage currents may be flowing in this circuit also, but. their value is sufficiently small to be negligible.

While I have shown the ammeter 30 as providing some use for the current flowing in the mechanically rectified circuit 29, 30, 3|, it should be understood that is merely for purposes of illustration. Obviously, the means 30 may be used merely to indicate the true load current so that it may be read by an operator. It is equally obvious, however, that the current flowing in the circuit 29, 30, 3| may be utilized for any control purpose desired and I do not wish to be limited in the application of my invention to the use of this current merely to operate an indicating de- Vice. 7

In the modification shown in Fig. 3 I have illustrated somewhat diagrammatically the use of a mechanical rectifier of the vibratory type in place of the rotary rectifier first described. It should be understood that this modification is utilized in connection with the transformer |3 supplied from source LI, L2, the tube rectifier, the X-ray tube I9, and all of its operating circuits, as described in connection with the first modification, down to and including the split secondary circuit of the transformer 23, 24 grounded .at 25. In other words, Fig. 3 merely indicates another type of mechanical rectifier which may be inserted in the circuit between the leads 23 and 24.

Obviously, any suitable vibratory rectifier might be used, but I haveillustrated the rectifier of Hans Pfannenmuller as disclosed in United States Patent 1,931,267, granted October 17, 1933. It is sufilcient to state here that the fixed contact 39 is elecrically. connected through the bracket 43 with the lead 23. The movable contact 4| is connected with the lead 24 through meter 42. The shunt resistor 43 is connected between the leads 23 and 24. The vibrator is energized from the source L|, L2 which is the same source as is connected to the transformer primary |3a. A phaseshift unit 44 permits the establishment of the proper phase relation between the actual switching period of the contacts 39, 4| and the X-ray tube current.

When the phase has been properly adjusted in the device of Fig. 3, the contacts 39 and 4| will be closed for a half wave cycle giving the currents A and B as described previously in connection with Fig. 2. During the next half wave period the contacts 39, 4| will be open. This action alternates continuously. It is obvious that the capacity current B again cancelsitself out, and the current A will be read on the meter 42 or may be utilized for a control device, if desired, as previously explained.

In the form of my device shown in Fig. 3, only half of the current is flowing through the meter 42 because only every other half wave is connected through the rectifier unit, therefore, if the meter 42 is to read full current it will have to be properly calibrated.

.What I claim In the combination of an X-ray tube having an anode and a cathode, a transformer having a primary adapted to be connected with a source of alternating electric current, tube rectifiers, said transformer. having a secondary, connected with said rectifiers, said rectifiers having aWheatstone bridge connection with said anode and cathode to supply rectified current thereto, said secondary being split to provide a central secondary circuit, said circuit being, grounded; the improvement consisting of a milliammeter in said central secondary circuit, a half wave rectifier of the polarized vibratory type in said central secondary circuit in series with said milliammeter, said vibratory rectifiers having'a pair of contacts, a shunt resistor in said centralsecondary circuit bypassing said contacts and said milliammeter, an electrical energizing circuit for said vibratory rectifier, phase shift means in said energizing circuit for said vibratory rectifier synchronizing the closing cycle of itscontactsrelative to the phase of the X-ray tube load so that said contacts close said central secondary circuit during one exact half cycle through said'milliammeter and so that said contacts are open during the other half cycle, :whereby current in said central secondary circuit then bypasses said contacts and said milliammeter through said shunt resistor, whereby onehalf of the true X-ray tube current is registered by said milliammeter and the. capacity component of the current in said central secondary circuit is balanced out.

LOUIS L. WEISGLASS.

REFERENCES CITED The following references are of record in the file of this patent: a V

UNITED STATES PATENTS Weisglass June 22, 1943 

